1. Field of the Invention
This invention relates to an improved particle and the methods of making same, the particle being characterized as being extremely hard and abrasive, while also having improved surface capillarity. More particularly, but not by way of limitation, the invention relates to an improved particle comprising a plurality of crystals connected together by a bonding material that has been partially removed to provide surface capillarity. The resulting particle is one which affords improved mechanical, chemical and vacumatic bonding as the particle is added to an elastomeric material.
2. Description of the Prior Art
There have been many developments in the art of tire manufacturing and other uses of elastomers to improve the life cycle and/or traction ability of an article as the surface of that article is in contacting engagement with a foreign surface. It is known that high product wear occurs in such operations as: a tire in rolling or braking engagement with a road surface; a conveyor belt carrying objects up or down an incline; and, pulley belts operating under heavy surface loads. These are given by way of example only, and by no means do these exhaust the myriad of resilient material usages that have been improved by the addition of abrasive particulate matter to elastomeric materials.
There are two reasons for adding an abrasive material to resilient material that will be considered herein. The first reason is to provide articles made from elastomeric material that have particles dispersed within the elastomer wherein there is low bonding strength to the elastomer. As the surface of the elastomeric article wears away (such as when a tire tread wearingly contacts a road), successive layers of elastomer are exposed; as each layer is exposed, a number of the particles are brought to the surface. Since the particles have low bonding strength to the elastomer, they fall away, and the surface is marked by voids left behind by the removed particles. This kind of phenomenon gives roughened surfaces and improved gripping effectiveness, and an automobile tire made of this type of elastomer-particle material experiences increased traction with a highway surface. Examples of particles used in elastomeric materials to give this result are wood, cork, salt and sand.
The second reason, to which reference was above made, for adding particulate matter to resilient material is the provision of hard abrasive particles in an elastomeric matrix that are disposed at the surface of resilient material, and which are bonded to the resilient material with bond strength sufficient to hold the abrasive particles to the surface in the face of wear forces. The abrasive surface exposed in carbide impregnated tires demonstrates this kind of elastomer wear surface. Not only is tire traction increased, but under proper usage, tire life is increased. Exceptions to the latter occur when internal fretting by sharp, jagged edges leads to early expiration of the elastomeric article due to loss of strength effected when the article relieves internal stresses by developing shear planes that separate.
Numerous teachings are available in the prior art that rely upon one or both of the above described phenomena, and which discuss other reasons for adding particulate matter to elastomers as well as discussing the many problems encountered in the utilization of a particle-elastomer matrix. Examples of such are found in U.S. Pat: Nos. 3,062,255, issued to Clark et al.; 1,175,624, issued to Fawkes; 1,266,100, issued to Brown; 2,472,331 issued to Koehler; 3,093,601, issued to Gessler; 3,165,487, issued to Gardner; 3,386,840, issued to Gruber; 3,442,053, issued to Henderson; 3,462,516, issued to Smith; 3,484,405, issued to Seto; 3,507,818, issued to Roach; 1,330,973, issued to Bartholomew; 1,330,988, issued to Sayre; 2,552,500, issued to Doenhoff; 2,675,047, issued to Andy; 2,727,935, issued to Kloepfer; 2,752,979, issued to Knill, 1,412,744, issued to Hobson et al.; 1,688,491, issued to Raoul; 1,578,121, issued to Haw; 993,222, issued to Busby; 1,250,405, issued to Williams; 2,467,418 issued to Alexiadis; 2,672,910, issued to Corson; 2,690,461, issued to Steeves; 1,290,576, issued to Kendall; 1,978,301, issued to Fisher; 2,011,496, issued to Luchinger; 3,227,200, issued to Andy; 2,961,026, issued to Stanton; 1,088,845, issued to Stromeyer; 2,766,800, issued to Rockoff; and 3,666,613, issued to Beninga.
The problems encountered in the prior art include that of the selection of an ingredient that can be added to an elastomeric material that will provide adequate bond strengths at the particle-elastomer interface while not introducing internal stress as above described. Ceramic materials have been involved in many attempts in the particle-elastomer art, as is clear from the above cited prior art, but such attempts have found that the addition of alumina and the like to elastomers has met with but limited success. This is attested to by the U.S. Pat. to Beninga, No. 3,666,613, which is a teaching of how to overcome low mechanical ceramic-elastomer bond strength by coating sintered ceramic objects with a thin layer of metal. The metal is chemically bonded to the ceramic surface, and the elastomer mechanically bonds to the metal layer.
Another problem is the selection of particles that do not retain gases or moisture that are freed when the elastomer is subjected to a heated environment or otherwise meets conditions conducive to effect such escapement. When this happens, the particle may be forcefully separated from the surrounding elastomeric material. If that occurs, any method designed to increase the bond strength between the particle and the elastomer is defeated in its purpose.